Download Neurons & the Nervous System

The Nervous System
The Nervous System
 the
electrochemical
(chemical reactions brought
about by electricity)
communication system of
the body
Neuron
 cells
of the nervous system
(brain, spinal cord, nerves)
 Neurons
perform three basic tasks:
 receive
information
 carry information
 pass information to the next neuron
Neuron Development
birth
3 months
2 years
Parts of the Neuron
Dendrites DETECT
Parts of the Neuron
Parts of the Neuron
Parts of the Neuron
Parts of the Neuron
Dendrites DETECT
Axons ANNOUNCE
Neurons
Neural Communication:
The Neural Impulse
Action Potential
 brief
electrical charge that travels down
the axon
All-or-None Principle
 if
a neuron fires it will always fire at the
same intensity
 doesn’t
matter if there is a strong or weak
stimulation
Refractory Period
 “recharging
phase” when a neuron, after
firing, cannot generate another action
potential
 once
complete the neuron can fire again
Resting Potential
 neuron
is at rest & capable of generating
an action potential
 neuron
is set and ready to fire
How are the 3 phases of neuron
communication like a toilet?
Action potential –
when you flush an
“impulse” is sent
down the sewer
pipe
Refractory period –
delay after flushing
when the toilet can
not be flushed again
Resting Potential –
toilet “charged” when
there is water in the
tank and is capable
of being flushed
again
All-or-none-principle –
always flushes with the
same intensity no
matter how much force
you apply to the handle
Review Questions
(think! don’t say the answer out loud…yet)
1.
What are the three phases of
communication within a neuron?
2.
What is the all-or-none principle?
Communication
Between Neurons
“How do messages travel
from one neuron to the next?”
Synapse

neurons do not come
into contact with each
other

Synapse - tiny, fluid
filled gap between the
axon terminal of one
neuron and the dendrite
of another neuron
Neurotransmitters

chemical messengers

travel across the synapse

fit into receptor sites on the
dendrite of the next neuron
Neurotransmitters

can stay only in receptor
sites designed to fit their
shape

serve two functions:
1.
2.
Excitatory Effect
Inhibitory Effect
Excitatory Effect
 makes
it MORE
likely that the
receiving neuron will
generate an action
potential
Inhibitory Effect
 makes
it LESS likely
that the receiving
neuron will generate
an action potential
Neurotransmitters
Review Questions
(think! don’t say the answer out loud…yet)
1.
How do messages travel from one neuron to
the next?
2.
How do neurotransmitters that have an
excitatory effect impact neurotransmission?
What about an inhibitory effect?
Neurotransmission
Simulation
http://www.brainexplorer.org/neurolo
gical_control/Neurological_Neurotran
smission.shtml#
The Central &
Peripheral Nervous
Systems
The Nervous System
Central Nervous System (CNS)

brain & spinal cord

brain: where most
information
processing takes place

spinal cord: main
pathway information
follows as it enters &
leaves the brain
Spinal Cord
Divisions of the Nervous System
Peripheral Nervous System (PNS)

all the nerves that
feed into & branch
out from the brain &
spinal cord
Divisions of the Nervous
System
Somatic Nervous System
 contains:
motor nerves
 controls:
voluntary movements of skeletal
muscles
Divisions of the Nervous
System
Autonomic Nervous System
 Controls:
glands & muscles of the
internal organs
 monitors
the automatic functions
(breathing, blood pressure, and digestive
processes)
Divisions of the Nervous
System
Sympathetic Nervous System
 controls:
arousal
 fight-or-flight
response prepares
the body to deal with
threats or challenges
Divisions of the Nervous
System
Parasympathetic Nervous System
 controls:
calming
 brings
the
body back to a
relaxed state
Divisions of the Nervous System